#include <stdio.h>

int binarySearch(int arr[], int target, int n) {
    int left = 0;
    int right = n - 1;
    while (left <= right) 
    {
        int mid = (left+right)/2;
        if (arr[mid] == target) 
        {
            return mid; 
        } 
        else if (arr[mid] < target) 
        {
            left = mid + 1; 
        } 
        else  
        {
            right = mid - 1; 
        }
    }
    return -1;
}

int main() {
    int arr[] = {1, 3, 5, 7, 9, 11, 13};
    int target;
    int n = sizeof(arr) / sizeof(arr[0]); 

    scanf("%d", &target);

    int result = binarySearch(arr, target, n);
    if (result != -1) {
        printf("%d\n",result);
    } else {
        printf("Not Found\n");
    }

    return 0;
}